The research discusses an important issue of war, which is the declaration of war before starting it, addressing the problem that some people think that the wars carried out by Muslims are illegal and unjust and represent an attack on others, The article aims to show the correct picture of this, the Islamic religion does not provoke war, and does not like it, but resorts to it compulsorily, and this is evidenced by what came in the research from the controls and values set by Islam to try to avoid war as much as possible, and among these values ( permission to fight), so the research dealt with the methods, Citing practical models , the article explained that Sharia is fair in its wars, it works to save blood, even if it is for the enemy, and this is the general feature of Sharia, The research shows that those moral values that Islam seeks to achieve are human values that serve all humanity, as Sharia is elegant and wise in its war, As for the cases of unjust war that happened, this was not ordered by Islamic law and does not satisfy it, The article was based on the analytical method of collecting the texts of the Islamic Sharia received on the call before the fighting, as well as using the historical method in the practical facts in which Muslims worked for the cause of declaring war, As a result of this article, the war among the followers of Islam is a legitimate war, not an aggressive one, according to the Sharia, which requires preventive measures before the start of the war in order to save blood, so this contributed to finding peaceful solutions, achieving the benefit of the people.